1. Field of the Invention
The present invention relates to medical devices and, more particularly, to apparatus and methods for the reduction and fixation of fractures.
2. Description of the Related Art
When a fracture is repaired, the bone fragments are placed in appropriate alignment in an anatomically correct position (reduction). Following reduction of the fracture, the fracture is then fixated, meaning that the bone fragments are prevented from moving from the reduced placement during the healing process. Various apparatus such as bone plates, bone screws, and rods are used for fixation of bone fragments. Following fixation, the fracture is then allowed to heal. After the fracture has healed, the fixation apparatus may be removed or may be left permanently in the body.
Bone plates, which are typically thin and have a plurality of fastener openings for fastening by various fasteners such as bone screws to the bone surface, are often used in cranial and maxillofacial surgery. For example, the repair of mandibular fractures often involves reduction and fixation by various bone plate systems. A surgeon will likely require assistance from one or more additional surgeons or surgical assistants in order to effect repair of a mandibular fracture by using a bone plate or bone plating system. One and, sometimes, two assistants must hold the bone fragments in reduction while the surgeon fixates the fracture by fastening the bone plate or bone plate system. Large incisions may be required in order to surgically fix a mandibular fracture with a bone plate or bone plate system, which can result in damage to blood vessels, especially the blood vessels that supply the bone, thereby interfering with the bone healing process. Nerve damage may also occur. The bone plate must be shaped to fit the bone in the region of the fracture. The shaping and fitting process, which generally involves trial and error, is conducted in the operating theater by the surgeons, and can be time consuming thereby lengthening the time the patient spends under anesthesia. A bone plate does have the advantage of providing sufficient structural support across the fracture so that, when a bone plate or bone plate system is used to fixate a mandibular fracture, the patient may be able to resume some normal eating requiring mastication following the surgery.
Reduction of a fracture may also be accomplished using a reduction wire and bone screws. When a reduction wire and bone screws are used to reduce and fixate a fracture, two bone screws are placed in the bone, one bone screw on each side of the fracture. The bone screws are only partly tightened down. A wire loop in then passed around the bone screws such that the wire fits under the heads of the bone screws, the bone screws having been placed such that the wire is perpendicular to the fracture. The surgeon then reduces the fracture by applying tension to the reduction wire by pulling on the reduction wire, which draws the bone fragments together. After reduction of the fracture, the wire may be further looped around the bone screws. Then the bone screws are tightened to clamp the wire between the bone and the screw heads thereby fixating the fracture. Looping the wire around bone screws with countersink heads will further reduce the separation of the fracture because the tension in the wire is increased as the bone screws are tightened down and the wire loops around the bone screw shafts are pushed onto the conical countersink. Use of a reduction wire and bone screws has been described for reduction and fixation of a mandibular fracture. See, for example, R. Wang et al., Arch. Otolaryngol. Head Neck Surg. 124, (1998) pp 448-452. While Wang et al. describe the use of 24-gage stainless steel wire and 2 mm diameter, 4-6 mm in length monocortical bone screws placed 4 to 6 mm from the fracture, nails or other fasteners could be substituted for the bone screws and a variety of wires and other ligatures could also be used.
Unlike the installation of a bone plate, a single surgeon may perform a fracture reduction and fixation by using a reduction wire and bone screws. Use of a reduction wire and bone screws requires a smaller incision resulting in less nerve and vascular damage than installation of a bone plate. This procedure may be quicker than installation of a bone plate, which reduces the patient's time under anesthesia.
However, a non-chewing diet is required following the use of a reduction wire and bone screws for reduction and fixation of a mandibular fracture. Furthermore, reduction wire and bone screws may only be used to reduce and fixate certain types of fractures. A reduction wire and bone screws is best applied to simple fractures perpendicular to the cortices or with interlocking fracture surfaces. A reduction wire and bone screws is usually not applicable to the repair of comminuted fractures or to the repair of oblique unstable fractures where the reduction wire might tend to further distract the fragments. Oblique unstable fractures are usually best repaired using bone plates or other apparatus.
Existing bone plates and bone plate systems for internal reduction and fixation of fractures, such as mandibular fractures, require a large incision, multiple surgeons or a surgeon plus at least one assistant, and lengthy anesthesia with concomitant risks and insults to the body. Simpler apparatus, such as reduction wire and bone screws, may be installed quickly by a single surgeon with a smaller incision than that required for installation of a bone plate or bone plate system. However, use of a reduction wire and bone screws does not give the structural support that a bone plate or bone plate system gives so that, in the case of mandibular fractures, the patient must follow a restricted diet of foods that do not require chewing for several weeks following surgery. A reduction wire and bone screws cannot be used to repair certain types of fractures. A bone plate or bone plate system must be used. Thus, it is seen that currently available apparatus for fracture reduction and fixation have a variety of shortcomings. Therefore, a need exists for an apparatus that can be installed by a single surgeon, that minimizes the size of the required incision, that gives the support to the fracture of a bone plate, and that has the ability to fixate the range of fractures that may be fixated by a bone plate.